This article presents a survey of male dogs treated with the gonadotropin releasing hormone (GnRH) agonist deslorelin (Suprelorin®, Virbac) at three animal clinics in central Sweden. Filled-in questionnaires from 110 dogs were received. The paper also includes a review of existing litterature concerning reproduction in male dogs, focusing on endocrinology, the effects of gonadectomy and the GnRH agonist deslorelin. Continuous treatment with deslorelin produces infertility in male dogs. The pituitary is initially stimulated by deslorelin leading to a rise in luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion. As a consequence the testosterone levels also increase temporarily.